The biological and chemical sciences, much like the electronics industry, have sought to gain advantages of cost, speed and convenience through miniaturization. The field of microfluidics has gained substantial attention as a potential solution to the problems of miniaturization in these areas, where fluid handling capabilities are often the main barrier to substantial miniaturization.
For example, U.S. Pat. Nos. 5,304,487, 5,498,392, 5,635,358, 5,637,469 and 5,726,026, all describe devices that include mesoscale flow systems for carrying out a large number of different types of chemical, and biochemical reactions and analyses.
Published international patent application No. WO 96/04547 to Ramsey describes microfluidic devices that incorporate electrokinetic means for moving fluids or other materials through interconnected microscale channel networks. Such systems utilize electric fields applied along the length of the various channels, typically via electrodes placed at the termini of the channels, to controllably move materials through the channels by one or both of electroosmosis and electrophoresis. By modulating the electric fields in intersecting channels, one can effectively control the flow of material at intersections. This creates a combination pumping/valving system that requires no moving parts to function. The solid state nature of this material transport system allows for simplicity of fabricating microfluidic devices, as well as simplified and more accurate control of fluid flow.
Published international patent application No. 98/00231 describes the use of microfluidic systems in performing high throughput screening of large libraries of test compounds, e.g., pharmaceutical candidates, diagnostic samples, and the like. By performing these analyses microfluidically, one gains substantial advantages of throughput, reagent consumption, and automatability.
Another advantage of microfluidic systems is to provide the ability to integrate large numbers of different operations in a single "lab-on-chip" device, for performing both upstream and downstream processing of reactants for analysis and/or synthesis. For example, International Patent Application No. PCT/US98/17910, filed Aug. 27, 1998, describes devices and systems that elegantly control and monitor temperature within microfluidic systems by applying electric currents to fluids to generate heat therein, as well as measure solution conductivity as a measure of fluid temperature.
Despite the substantial advantages made in the field of microfluidics, improvements are always desirable which allow more simplistic integration of analytical and synthetic operations. The present invention meets these and a variety of other needs.